This study will investigate the processes leading to the association between behavior and emotional problems and school achievements in grade school children. It will extend previous research by focusing on several issues that have not been adequately addressed. Among these issues are the changes in the association behavior/emotional problems with achievements over the duration of middle childhood. More importantly, there is limited understanding of the processes that lead to the cycle of behavior /emotional problems and low achievement. Information is needed on factors that might mediate or break the cycle of behavior/emotional problems and low achievements. Basic research on this issue will pave the way to develop better intervention programs that are developmentally appropriate and that target specific groups of children. Previous research indicates that there may be some sex differences in the association between behavior/emotional problems and achievement. Understanding of the specific processes that lead to these differences is key to the development of interventions that may help both boys and girls. The investigators propose to conduct a study to address these issues. They will investigate four alternative mechanisms that may lead to the association between behavior/emotional problems and achievement: (1) Behavior/emotional problems may affect school achievements. This is partly because behavior/emotional problems may interfere with the learning process and lead to poor relationships with teachers. (2) Achievement problems may affect behavior/emotional well being. This is partly because achievement deficits may result in frustration, negative self-concept, and school detachment. (3) Behavior/emotional problems and achievements problems may be the outcomes of common early physiological and heritable factors. The investigators will identify the roles of the specific processes that link behavior/emotional problems and achievement that may differ in boys and girls. In order to accomplish the goals of this study, the investigators propose to use extant data from two studies: the Children of the National Longitudinal survey of Youth (NLSY), providing four longitudinal assessments of children from preschool through middle childhood, supplemental in a limited way by the new Panel Study of Income Dynamics Child Supplement (PSID-CS), Complementary strengths of these data sources will be exploited.